kit building, tail vs nose weight
 

Just started building a dynaflight Butterfly.. 99" wingspan powered glider.
I'm trying to keep the tail light as like most models, I read about having to add nose weight after the build.

While sanding the taper on the back end of the elevator, I saved the saw dust and found I have removed 4+ grams just by sanding.

isnt there a formula where if you remove 1 gram from the tail, that would be 3 grams of weight you wont have to add to the nose??? of something like that???

I've always built heavy so I'm makeing an effort to keep the plane/tail as light as I can...

where can I get the most weight savings.... I've been using CA so far..???

thanks


Steve

RE: kit building, tail vs nose weight
 

I have no idea...What I do is before I cover the model I move stuff around to get to CG. You can't have a formula as the distance to the tip of the tail from the CG is longer or shorter depending on the airpalne

RE: kit building, tail vs nose weight
 

The golden rule that has worked for me is one on the tail, four on the nose......Good Luck, Dave

RE: kit building, tail vs nose weight
 

G'day

I have had two Butterflys. Great planes.

As for the way to calculate the difference - if you measure from the CG to where the weight in the tail is and multiply the weight by the distance, then an equivalent weight on the front will be the distance to the weight on the front by the weight.

So if you remove 5 grams from the tail and it is .5 metre back from the CG then it creates a moment of 5gm x 0.5 metre or 2.5 gm.metres. Then to balance it on the nose at say a distance of .2 metre you need a weight such that 0.2m x WEIGHT = 2.5. WEIGHT then works out at 2.5 / .2 or 12.5 gm

All these numbers are just made up but you can see from this rough example that you need 12.5 grams at the front to balance 5 grams at the back.

Did this help at all?

Basically to make a beam balance the weight x distance from the centre must be the same on both sides.

Mike in Oz

RE: kit building, tail vs nose weight
 

What Mike109 said in a picture. Yes, I did this in MSPaint:)

RE: kit building, tail vs nose weight
 

Thanks guys. Took off another 4-5 grams of the rudder last night. Agin, just want to minimize the weight I will need in the nose...

Steve

RE: kit building, tail vs nose weight
 

G'day

Thanks for Mr Stang for the picture. They really are worth a thousand words.

My first Butterfly had an OS 26 four stroke in it. I was worried it would not be enough as a hobby shop man told me his had an OS 25 two stroke in it. I need not have worried. The little four stroke was perfect as it was happy to idle for long periods while I glided around with the Butterfly. It would stay up for ages. The longest flight was about 45 minutes and I only came down then because another person wanted the frequency I was using.

My current one originally had another 26 in it but it now has a Saito 30. If I were building one these days, I would seriously consider making it electric for two reasons. (1) it would stay cleaner and (2) the ability to stop and start the motor is a real advantage with a plane like the Butterfly. It really is a glider and flies much better as a glider than when it is under power.

It was also the first plane I landed. I was still very much learning to fly and yet on its first flight I landed it. They are really brilliant planes when used the way they are intended.

Cheers

Mike in Oz

RE: kit building, tail vs nose weight
 

Some years back a Butterfly was the first airplane I ever tried doing arrested carrier landings with.

It had a K&B .28 Sportster on it and just drilled a hole through the after fuselage then inserted a long music wire through a piece of brass tube in the fuselage. Bent this back and down tied together about a foot long with a hook bent into the end. Just let this drag on takeoff.

The Independence class carrier was two milk jugs with fifty feet of mason line tied to the handles and stretched across the runway (uh deck).

Butterfly seemed an odd choice but what fun and it was no Piece-O-cake either (pun intended):D


John

RE: kit building, tail vs nose weight
 

G'day

No "piece-o-cake". Ho Ho Ho. Very punny indeed.

When I turned up with my first Butterfly, one of the older members asked whether is was a Piece-O-Cake which is its little .049 powered sibling. When he found it was a Butterfly he was immediately impressed and told me that I had a "real aeroplane". He then helped me with the first flight and later taught me how to fly it as a glider. Great days.

My actual instructor hated it. Too slow. He liked his Thunder Tiger Eagle 40 with a Rossi 60 in it. As a result, he kept steering me away from planes like the Kadet Senior (which I eventually found for my self) to things that he liked to fly but I could not fly. So I spent quite a while flying the Butterfly and building up my confidence. Then I found the Kadet Senior and I was off.

Cheers

Mike in Oz